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Added analogue scaling & averaging; discrete check reads

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Added input scaling function and averaging of multiple readings for
noise reduction to the analogue input node.
Added the ‘sanity check’ read of the digital input pin to the timer
callback in the discrete input node
This commit is contained in:
Maxwell Hadley
2014-02-12 22:27:08 +00:00
parent 955fd1ad46
commit f46b59d69f
3 changed files with 65 additions and 53 deletions
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47
hardware/BBB/144-analog-in.js
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@@ -33,30 +33,49 @@ function AnalogInputNode(n) {
this.topic = n.topic;
this.pin = n.pin;
this.breakpoints = n.breakpoints;
this.averaging = n.averaging;
if (this.averaging) {
this.averages = 10;
} else {
this.averages = 1;
}
// Define 'node' to allow us to access 'this' from within callbacks (the 'var' is essential -
// otherwise there is only one global 'node' for all instances of AnalogInputNode!)
var node = this;
node.log("breakpoints:");
for (var i = 0; i < node.breakpoints.length; i++) {
node.log(i + ": {input:" + node.breakpoints[i].input + ", output:" + node.breakpoints[i].output + ", mutable:" + node.breakpoints[i].mutable +"}");
}
// A callback function variable seems to be more reliable than a lambda ?!
var readCallback = function (x) {
var msg = {};
msg.topic = node.topic;
msg.payload = x.value;
if (isNaN(x.value)) {
node.log(x.err);
// Variables used for input averaging
var sum; // accumulates the input readings to be averaged
var count; // keep track of the number of measurements made
// The callback function for analogRead. Accumulates the required number of
// measurements, then divides the total number, applies output scaling and
// sends the result
var analogReadCallback = function (x) {
sum = sum + x.value;
count = count - 1;
if (count > 0) {
bonescript.analogRead(node.pin, analogReadCallback);
} else {
var msg = {};
msg.topic = node.topic;
sum = sum/node.averages;
// i is the index of the first breakpoint where the 'input' value is strictly
// greater than the measurement (note: a measurement can never be == 1)
var i = node.breakpoints.map(function (breakpoint) { return sum >= breakpoint.input; }).indexOf(false);
msg.payload = node.breakpoints[i-1].output + (node.breakpoints[i].output - node.breakpoints[i-1].output) *
(sum - node.breakpoints[i-1].input)/(node.breakpoints[i].input - node.breakpoints[i-1].input);
node.send(msg);
}
node.send(msg);
};
// If we have a valid pin, set the input event handler to Bonescript's analogRead
if (["P9_39", "P9_40", "P9_37", "P9_38", "P9_33", "P9_36", "P9_35"].indexOf(node.pin) >= 0) {
node.on("input", function (msg) { bonescript.analogRead(node.pin, readCallback) });
node.on("input", function (msg) {
sum = 0;
count = node.averages;
bonescript.analogRead(node.pin, analogReadCallback);
});
} else {
node.error("Unconfigured input pin");
}